1. Field of the Invention
The present invention relates to methods and compositions for the treatment of plants to reduce injury due to exposure to polluted air, and more particularly to the application of compositions to plants to minimize or prevent air pollution stress injuries. The present invention further relates to the treatment of plants which have been subjected to injury due to exposure to air pollutants.
2. Description of the Prior Art
Plants are subject to exposure to a variety of external stresses. Air pollution, for example, can significantly affect the growth of plants. It is desirable to treat plants to avoid or reduce any detrimental effects that would otherwise result.
In sufficient concentrations, air pollutants injure plant foliage, significantly alter growth and yield, and thereby can change the quality of marketable plant products. For example, exposure to ozone in concentrations of 0.05 to 0.12 ppm (by volume) for 2 to 4 hours injures leaves of the most sensitive cultivars. During the summer months, the atmosphere over some areas of the U.S. contains levels of ozone ranging from 0.05 to 0.10 ppm (by volume). As reported by the National Loss Assessment Network, crops such as beans, soybeans, peanuts, tobacco, and cotton suffer significant yield losses at these ozone concentrations. Ozone affects vegetation throughout the United States, impairing crops, native vegetation, and the ecosystem more than any other air pollutant.
In addition to ozone, major air pollutants damaging to crops include: peroxyacetyl nitrate, oxides of nitrogen, sulfur oxide, fluoride, agricultural chemicals, and ethylene and other hydrocarbons. Ozone and sulfur dioxide account for 90% of crop damage caused by air-borne pollutants. However, the additional pollutants listed, as well as others, also contribute to crop damage and losses. It has been estimated that American farmers lose $3 billion a year in damaged crops due to air pollution alone.
Although there are chemicals which have been reported to reduce injury to plants due to air pollution, none yet has been of practical utility. For example, scientists reported in 1986 that the injection of ethylene diurea (EDU) into the stem of shade trees could protect the trees from ozone damage. EDU was also determined to be a growth regulator. Test results at that time indicated that EDU altered enzyme and membrane activity within the leaf cell where the photosynthesis of the plant takes place. Under the laboratory conditions, a single soil drench of the EDU was effective in providing protection against acute exposure to ozone. However, the efficacy of the compound for field application has not been established.
In order to be practically useful, a chemical composition must be non-toxic to the plants, environmentally acceptable and relatively inexpensive. The present invention satisfies these requirements and provides for the protection of plants from ozone and other forms of air pollution stresses.